Abstract Cell therapies have been held back by serious challenges in achieving speci?c delivery to the damaged organ, realizing treatment ef?cacy, and safety concerns. A noninvasive imaging technique that could follow a sub-therapeutic dose (say 10 cells) anywhere in the body, and report back on the cells' viability, could greatly expedite protocol optimization and hasten cellular therapy clinical adoption. Today's whole-animal cell tracking imaging methods (e.g., MRI, optical, ultrasound, nuclear medicine) all have their strengths and technical limitations. A new noninvasive imaging method called Magnetic Particle Imaging (MPI) uses zero radiation. MPI shows extraordinary promise as a complementary cell tracking and reporting method. Just to be clear, MPI images cannot be obtained in an MRI scanner. This year, our group at Berkeley showed MPI tracking of stem cells for the ?rst time in live animals, with quantitative 200-cell ?positive contrast? sensitivity. MPI shows ideal, quantitative contrast with no confounds near air or bone as in other modalities. MPI is already 100-times more sensitive than today's noninvasive cell imaging methods, and here we aim to make it even more sensitive. Both the 200-cell sensitivity and MPI's spatial resolution can still be greatly improved. Our overall aim is to improve MPI to reach the true physics limits of MPI, speci?cally 20-cell detection and 280-micron spatial resolution. Finally, we plan to validate these innovations by tracking an in vivo model of stem cell treatment for demyelinating disease with stem cell expert, UC Berkeley Professor David Schaffer.